This application claims priority to prior application JP 2002-20312, the disclosure of which is incorporated herein by reference.
This invention relates to an optical pickup unit, which is contained in an optical disc drive, for recording/reproducing data in/from an optical recording medium such as an optical disc and, in particular, to a lens holder for fitting a lens installed in an optical base of the optical pickup unit.
In the manner known in the art, an optical pickup unit (which is also called xe2x80x9cOPUxe2x80x9d) is a unit for converging a laser beam produced by a semiconductor laser serving as an optical source on a signal recording surface of an optical disc through an objective lens and for detecting a return beam from the signal recording surface by a photo detector serving as optical detecting means.
The optical pickup unit comprises various optical parts which are installed in an optical base. There is a lens called a beam spread lens as one of the optical parts.
On assembling the optical pickup unit, in order to correct degradation of an optical characteristic caused by assembling errors, it is well adopted (used) a method of adjusting a position of the beam spread lens and of fixing the beam spread lens in the optical base using adhesive. Inasmuch as the beam spread lens has a concave surface, it is difficult to adjust the position of the beam spread lens as it is. Accordingly, by fitting the beam spread lens in a lens holder having a shape which is easy to adjust a position and by adjusting the position of the lens holder, it results in adopting a method of adjusting the position of the beam spread lens.
In the manner which will later be described in conjunction with FIGS. 12A and 12B, it is difficult for a known lens holder to move the lens holder only along an optical axis. As a result, a center axis of the beam spread lens is out of the optical axis on adjusting the position of the beam spread lens. Accordingly, an optical characteristic of the optical pickup unit is degraded.
It is therefore an object of this invention to provide a lens holder in which a center axis of a lens is not out of an optical axis on adjusting a position of the lens.
It is another object of this invention to provide a lens holder of the type described, which is capable of manufacturing an optical pickup unit having a good optical characteristic.
Other objects of this invention will become clear as the description proceeds.
On describing the gist of this invention, it is possible to be understood that a lens holder is for fitting a lens installed in an optical base of an optical pickup unit. The optical base comprises a base plate and a vertical wall perpendicularly extending upwards from the base plate. The lens holder is disposed in a corner portion formed by the base plate and the vertical wall. The lens holder is always pressed against the corner portion by a presser bar spring. The lens holder has an adjustment groove extending in a direction perpendicular to the vertical wall. The lens holder is moved along an optical axis of a laser beam by moving an adjustment pin with the adjustment pin inserted in the adjustment groove through a hole formed in the base plate, thereby adjusting a position of the lens. According to an aspect of this invention, the adjustment groove has a taper shape where a width thereof becomes narrower in proportion to near to the vertical wall and the width thereof becomes wider in proportion to apart from the vertical wall.
The afore-mentioned lens holder, the lens may be, for example, a beam spread lens for use in the optical pickup unit.